In recent years, techniques for proliferating or maintaining in vitro various organs, tissues and cells that play distinct roles in the body of animals and plants have been developed. Proliferation or maintenance of the organs and tissues in vitro is called organ culture and tissue culture, respectively, and proliferating, differentiating or maintaining in vitro the cells separated from an organ or tissue is called cell culture. Cell culture is a technique for proliferating, differentiating or maintaining separated cells in vitro in a medium, and is indispensable for detailed analyses of the in vivo function and structure of various organs, tissues and cells. In addition, the cells and/or tissues cultured by the technique are utilized in various fields for efficacy and toxicity evaluation of chemical substances, pharmaceutical products and the like, large-scale production of useful substances such as enzymes, cell growth factors, antibodies and the like, regenerative medicine supplementing organ, tissue and cell that were lost by disease and deficiency, improvement of plant brand, production of genetically modified products, and the like.
Animal-derived cells are broadly divided into non-adherent cells and adherent cells based on the properties thereof. Non-adherent cells are cells that do not require a scaffold for growth and proliferation, and adherent cells are cells that require a scaffold for growth and proliferation. Most of the cells constituting the living body are the latter, adherent cells. As culture methods of adherent cells, single layer culture, dispersion culture, embedded culture, microcarrier culture, sphere culture and the like are known.
It has been reported that static state suspension culture of animal and plant cells and/or tissues can be performed by mixing a structure containing a polymer compound having an anionic functional group, such as deacylated gellan gum and the like in a liquid medium, without substantially increasing the viscosity of the liquid medium and that the proliferation activity of the cells is promoted by culture using this medium composition containing the above-mentioned structure (patent document 1). In the medium composition, a polymer compound having an anionic functional group, such as deacylated gellan gum and the like, is linked via a metal ion (e.g., divalent metal ion such as calcium ion and the like) to form an indeterminate structure, which in turn forms a three dimensional network in the medium to provide a carrier for suspending cells and the like.